The "Heat index," the latest trend in weight loss. It's actually something used by the ancient Egyptians, a belly band you wear around your stomach. Shrink your waistline by preventing you from overeating. ABC's Mara schiavocampo checks it out. ? Reporter: It's the latest weight loss trend. No, not a juicer or insane workout but the malory band, a simple polyester cord designed to help you lose weight just by wearing it around your waist. As you eat your stomach expands and it makes the band start to feel tighter and that's an alert for your brain to say, I've had enough. Reporter: Penny pmalory says she was inspired after meeting a man who wore a piece of string around his waist to gauge how full he was getting. It gives you a constant gauge. There's no cheating. No lying to yourself. Reporter: This purported curve curber sells for 40 bucks and get this, it's meant to be worn 24/7. While you sleep, at the gym, even in the shower. It seems to be working for some. Mom Mary peacock has lost 16 pounds in nine months. It's like a psychological reminder. Reporter: 29-year-old Ashley sun derland is also a fan of the band. She lost 25 pounds in five months changing her eating habits and picking up yoga. It has really helped me recognize when enough is enough and when I'm full. Reporter: But not everyone thinks this string is a slimming solution. Really when it comes down to it it's calories that matter when it comes to weight loss. Reporter: So this is no different than an incentive of wearing smaller pants. Right. But personally I would rather wear a smaller size jeans or a smaller pair of pants than wearing a tighter polyester cord around my waist. The piece of string cannot make you lose weight but remind you and encourage you. Reporter: Unique idea that certainly is striking a cord. For "Good morning America," mar schiavocampo, ABC news, new York. I think it makes sense and you know when I was a gymnast back in the day, we had to wear bands around our stomachs -- if for the same reason. It was more for posture but a reminder to stay fit and so I remember my mom sewed a froggy on it to make me happier wearing split same is if your waistband is snug, you don't really want to eat. I do get it. Thanks, para. Up to robin and George right now.

This transcript has been automatically generated and may not be 100% accurate.

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